This invention relates to persistent screens for radiation images, and more particularly, the invention relates to screens which provide improved sharpness without a noticeable signal loss. Such screens of this general type are known for instance from European patent application No. 00 21 174.
The picture sharpness of persistent fluorescent screens which contain in their persistence layer as an active substance a barium halide, such as barium fluorochloride (BaFCl) or a barium fluorobromide (BaFBr), is measured, as a rule, with few line pairs (Lp) per millimeter, say 3 Lp/mm. To increase the definition according to the above-mentioned European patent application No. E-OS 00 21 174, dyes are admixed to the persistence layer. But the dyes or pigments used, which themselves show no light emission, unfortunately absorb light and thereby reduce the image signals produced during illumination.